NEW YORK ( TheStreet) -- Alibaba's initial public offering, Apple's iPhone launch and the ever-changing color of Fed Chair Janet Yellen's tea-leaves will be major stories to watch on Wall Street when traders return from their summer holiday after Labor Day weekend.

Alibaba will headline Wall Street activity after Labor Day, even if there are a few major M&A announcements and market hiccups on geopolitical unrest next week. The Chinese e-commerce giant is poised for what could be the largest ever stock listing on the New York Stock Exchange , and the company and its founder Jack Ma are expected to kick off their IPO roadshow just after Labor Day.

If all goes as planned Alibaba could begin trading by mid-September, in what many be an IPO for the ages. While Alibaba does over 90% of its business in China , the company's listing will be a major story for U.S. investors.

Yahoo! currently owns over 20% of Alibaba , meaning a strong or weak offering could impact the company' share price. CEO Marissa Mayer also hasn't yet indicated what Yahoo! might do with its Alibaba investment once the company becomes publicly traded. As TheStreet's Jim Cramer notes, Alibaba's extremely dominant e-commerce businesses in China and the company's high margins may attract investors in U.S. listed giants like Amazon and eBay .

Normally, Apple dominates tech headlines in the weeks after Labor Day as fans of the company await new smartphone and tablet products. While Apple has been mum on what it will unveil this year, the company did send out invites for September 9. "[W]ish we could say more," was Apple's message, adding further speculation a larger phone format may be released, along with some form of wearable product.

There's been a steady rise in sentiment about Apple's product pipeline and its stock in 2014, and the company's September event could prove an anchor for those expectations.

Merger Tuesday, Merger Monday

It won't shock any market watchers if there are a few deals that hit Wall Street as traders return from the beach on Tuesday. Last year, Verizon announced a $130 billion acquisition of its remaining interest in Verizon Wireless on the day after Labor Day, in the biggest M&A deal since the crisis.

Even without a major Labor Day merger, there will be plenty of deal activity to watch in September. Many large mergers such as AT&T's takeover of DirecTV , Comcast's acquisition of Time Warner Cable and Sysco's deal for U.S. Foods remain in regulatory limbo. Meanwhile, wireless carrier T-Mobile is still weighing whether to go at it independently or it it will partner with a telecom or cable giant.